1. Field of the Invention
This invention relates generally to a device and method adapted for use with oilfield pipe (xe2x80x9ctubularsxe2x80x9d). More specifically, the invention relates to a device and method used to plastically radially expand downhole tubular members in a wellbore.
2. Background Art
Casing joints, liners, and other oilfield tubulars are often used in drilling, completing, and producing a well. Casing joints, for example, may be emplaced in a wellbore to stabilize a formation, to protect a formation against elevated wellbore pressures (e.g., wellbore pressures that exceed a formation pressure), and the like. Casing joints may be coupled in an end-to-end manner by threaded connections, welded connections, and other connections known in the art. The connections may be designed so as to form a seal between an interior of the coupled casing joints and an annular space formed between exterior walls of the casing joints and walls of the wellbore. The seal may be, for example, an elastomer seal (e.g., an o-ring seal), a metal-to-metal seal formed proximate the connection, or similar seals known in the art.
In some well construction operations, it is advantageous to radially plastically expand threaded pipe or casing joints in a drilled (xe2x80x9copenxe2x80x9d) hole or inside a cased wellbore. In a cased wellbore, radially expandable casing can be used to reinforce worn or damaged casing so as to, for example, increase a burst rating of the old casing, thereby preventing premature abandonment of the hole. In open hole sections of the wellbore, the use of radially expandable casing may reduce a required diameter of a drilled hole for a desired final cased hole diameter, and may also reduce a required volume of cement required to fix the casing in wellbore.
In conventional oilfield drilling, casing strings are installed at regular intervals whereby the casing for the next interval is installed through the casing for the previous interval. This means that the outer diameter of a casing string is limited by the inner diameter of the previously installed casing string. Thus the casing strings in a conventional wellbore are nested relative to each other, with casing diameters decreasing in a downward direction.
Conventionally, an annular space is provided between each string of casing and the wellbore so that cement may be pumped into the annular space or annulus to seal between the casing and the wellbore.
Because of the nested arrangement of the casing strings in a conventional wellbore, and the annular space required around the casing strings for cement, the hole diameter required at the top of the wellbore is relatively large. This large initial wellbore diameter may lead to increased costs due to the expense of large diameter casing, the expense of drilling large diameter holes, and the added expense of cementing a large casing string.
In addition, the nested arrangement of the casing strings in a conventional wellbore can severely limit the inner diameter of the final casing string at the bottom of the wellbore, which restricts the potential production rate of the well.
It is desirable that a casing string can be radially expanded in situ after it has been run into the wellbore through the previous casing string, so as to minimize the reduction of inner diameter of the final casing string at the bottom of the wellbore. Radially expanding a casing string in the wellbore has the added benefit of reducing the annular space between the drilled wellbore and the casing string, which reduces the amount of cement required to effect a seal between the casing and the wellbore.
When a cold-forming expansion process is used (e.g., when a cold-forming expansion tool or xe2x80x9cpigxe2x80x99 is moved through a casing string so as to radially plastically expand the casing string), the casing string is usually run into the hole xe2x80x9cbox-downxe2x80x9d (e.g., the xe2x80x9cboxxe2x80x9d or female threaded connection is run into the hole facing downhole so that the expansion tool (xe2x80x9cpigxe2x80x9d) does not deform the xe2x80x9cpinxe2x80x9d nose or male threaded connection when the expansion tool is forced upward through the casing string). Note that tubular strings such as drill pipe, casing, or similar tubular members are normally run into the hole xe2x80x9cpin-downxe2x80x9d because it is easier to make up the threaded connections in the tubular string.
Various expandable casing techniques have already been developed. An expansion tool is typically used to plastically radially expand a string of casing or tubing disposed inside a wellbore from an initial condition (e.g., from an initial diameter) to an expanded condition (e.g., with a larger diameter). One common prior-art expansion process uses a conically tapered, cold-forming expansion tool (commonly referred to as a xe2x80x9cpigxe2x80x9d) to expand casing in a wellbore. The expansion tool is generally attached to a lower end of a casing string that is run into the wellbore. A leading mandrel of the expansion tool generally comprises a cylinder with an external diameter that is less than a xe2x80x9cdriftxe2x80x9d diameter of the made-up casing or tubing that is to be radially expanded. The expansion tool includes a tapered section having a taper angle that is generally between 5 degrees and 45 degrees. The expansion tool is generally symmetric about a longitudinal axis thereof. The expansion tool also includes a cylindrical section having a diameter typically corresponding to a desired expanded inner diameter of a casing string. The cylindrical section is followed by a tapered section.
After the casing string is set in place in the hole, usually by hanging-off the casing string from a casing hanger, a working string of drillpipe or tubing is run into the wellbore and attached to the expansion tool (e.g., the working string is generally attached to the leading mandrel). The expansion tool may also comprise an axial bore therethrough (not shown) so that pressurized fluid (e.g., drilling fluid) may be pumped through the working string, through the expansion tool, and in to the wellbore so as to hydraulically pressurize the wellbore. Hydraulic pressure acts on a piston surface defined by a lower end of the expansion tool, and the hydraulic pressure is combined with an axial upward lifting force on the working string to force the expansion tool upward through the casing string so as to outwardly radial displace the casing string to a desired expanded diameter. In this expansion process, a rate of radial expansion is determined by, for example, a total plastic strain required to expand the casing string, the taper angle, and a rate of axial displacement of the expansion tool through the casing string. Consistency of the expansion process is controlled by transitions along the expansion tool and a cross-sectional area of, for example, lengths of casing that form the casing string, threaded connections that couple the length of casing, and the like.
The expansion tool may be inserted into the casing string at either the bottom or the top, depending on the tool design and the application. Radial expansion may be performed at rates of, for example, 25 to 60 feet per minute. Other expansion processes, such as expansion under localized hydrostatic pressure, or xe2x80x9chydroforming,xe2x80x9d are known in the art, but are generally not used as much as the aforementioned cold-forming expansion process.
U.S. Pat. No. 5,348,095, issued to Worrall et al, discloses a method of creating a wellbore in an underground formation. A borehole is drilled in the underground formation, whereafter a casing of a ductile material is lowered into the borehole. The casing is selected to have a smaller elastic radial deformation than the surrounding formation when the casing is radially expanded against the borehole wall by application of a radial force to the casing. The radial force is applied to the casing so as to radially expand the casing against the borehole wall thereby inducing a plastic radial deformation of the casing and an elastic radial deformation of the surrounding underground formation, whereafter the radial force is removed from the casing.
U.S. Pat. No. 5,667,011, issued to Gill et al, discloses a method of creating a casing in a borehole formed in an underground formation. The method comprises the steps of (a) installing a tubular liner in the borehole, the liner being radially expandable in the borehole whereby the liner in its radially expanded position has a plurality of openings which are overlapping in the longitudinal direction of the liner, (b) radially expanding the liner in the borehole, and (c) either before or after step (b), installing a body of hardenable fluidic sealing material in the borehole so that the sealing material fills the openings and thereby substantially closes the openings. The sealing material is selected so as to harden in the openings and thereby to increase the compressive strength of the liner.
U.S. Pat. No. 6,012,523, issued to Campbell et al, discloses a downhole apparatus for use in expanding liner or tubing. The apparatus comprises a body for connection to a string and an expansion portion on the body. The expansion portion includes a plurality of radially movable parts for defining an outer surface thereof. The parts are initially arranged in an axially and circumferentially offset first configuration in which the parts may assume a smaller diameter first configuration. The apparatus is then run into a borehole and through a length of expandable tubing. The parts are then moved radially outwardly and axially aligned such that the parts assume a larger diameter second configuration and define a substantially continuous outer circumference. The expansion portion is then pulled through the tubing to expand the tubing.
U.S. Pat. No. 6,021,850, issued to Wood et al, discloses a method and apparatus of expanding tubulars. In the preferred embodiment, a rounded tubular is inserted through a larger tubular while suspended on a mandrel. A stop device, such as a liner hanger, is attached to the larger tubular after delivery downhole on the mandrel. Upon engagement of the liner hanger or other stop device to the larger tubular, the mandrel is freely movable with respect to the stop device. The mandrel contains a deforming device such as a conically shaped wedge located below the tubular to be expanded. A force is applied from the surface to the mandrel, pulling the wedge into the tubular to be expanded. When the wedge clears through the tubular to be expanded, it releases the stop device so that the stop device can be retrieved with the mandrel to the surface. Thus, the stop device is supported by the larger tubing while the smaller tubing is expanded when the wedge is pulled through it. Should the tubular being expanded contract longitudinally while it is being expanded radially, it is free to move away from the stop device.
U.S. Pat. No. 6,029,748, issued to Forsyth et al, discloses an apparatus and method that allow for downhole expansion of long strings of rounded tubulars, using a technique that expands the tubular from the top to the bottom. The apparatus supports the tubular to be expanded by a set of protruding dogs which can be retracted if an emergency release is required. A conically shaped wedge is driven into the top of the tubing to be expanded. After some initial expansion, a seal behind the wedge contacts the expanded portion of the tubing. Further driving of the wedge into the tubing ultimately brings in a series of back-up seals which enter the expanded tubing and are disengaged from the driving mandrel at that point. Further applied pressure now makes use of a piston of enlarged cross-sectional area to continue the further expansion of the tubular. When the wedge has fully stroked through the tubular, it has by then expanded the tubular to an inside diameter larger than the protruding dogs which formerly supported it. At that point, the assembly can be removed from the wellbore. An emergency release, involving dropping a ball and shifting a sleeve, allows, through the use of applied pressure, the shifting of a sleeve which supports the dog which in turn supports the tubing to be expanded. Once the support sleeve for the dog has shifted, the dog can retract to allow removal of the tool, even if the tube to be expanded has not been fully expanded.
U.S. Pat. No. 6,085,838, issued to Vercaemer et al, discloses a method of cementing a well permitting a reduction in the degree of diameter reduction of casing or liners required, and not requiring excessively large initial conductor casing. The method is characterized by provision of an enlarged wellbore and a novel liner structure which is adapted for expansion of a reduced diameter section thereof downhole, providing, before expansion of the section, unimpeded flow of fluid from the enlarged wellbore during cementing and close fit of the expanded section with the casing or preceding liner, after cementing is completed and expansion of the section. A novel well liner structure and novel well liner expansion means are also disclosed.
In one aspect, the invention comprises a tool for radially plastically expanding a pipe having a threaded connection therein, that includes a first section. The first section has an increasing diameter and increasing cone angle along a direction of travel through the pipe. The first section includes a first outer surface adapted to contact an inner surface of the pipe at a plurality of selected contact patches on the first outer surface. The tool also includes a second section axially disposed behind the first section along the direction of travel. The second section has an increasing diameter and decreasing cone angle along the direction of travel. The second section includes a second outer surface adapted to contact an inner surface of the pipe at at least one selected contact patch on the second outer surface.
In another aspect, the invention comprises a method of expanding casing comprising forcing a casing expansion tool through a casing segment. The casing segment has a smaller inside diameter than a largest outside diameter of the expansion tool. The expansion tool includes an outer surface, and a plurality of contact patches on the outer surface. The contact patches are adapted to contact a section of casing at a plurality of axial locations on the inside diameter of the casing.
In another aspect, the invention comprises a downhole apparatus including a casing expansion tool comprising an outer surface and a plurality of contact patches on the outer surface. Two adjacent contact patches define two circumferential contact surfaces having two different diameters. The apparatus also includes a section of casing. An inside surface of the section of casing is in contact with a plurality of the circumferential contact surfaces of the casing expansion tool on at least two axial locations.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.